Vehicle manufacturers are consistently turning to alternatives to vehicle fuel over the conventional gasoline engines that have fueled vehicles for almost a century. Several popular modern versions of alternative fuel vehicles include hybrid electric vehicles (HEVs) and electric vehicles (EVs).
In an HEV, a combination of gasoline and battery power are used to fuel a vehicle. It may be the case that gasoline is only used when battery power is depleted, or, alternatively, gasoline may be used at certain points during a trip to help recharge electrical system.
In an EV, the gasoline engine has been completely replaced with an electric engine. All power to the engine comes from an electrical source, which may be “recharged” partially during trips using regenerative systems, such as regenerative braking.
In both HEV and EV systems, the batteries that provide electric power to the vehicle hold a current “state-of-charge.” Representable as a percentage of a “full charge,” this state of charge is the electric equivalent to a “fuel tank level.”
Unlike conventional fuel-based vehicles, however, HEVs and EVs may have the ability to be “refueled” by simply plugging them in to an electrical outlet at a destination. Alternatively, they can be charged at electric refueling stations, although at this time a relatively low (compare to gasoline refueling stations) number of these stations exist.